Implantable neurostimulation systems have proven therapeutic in a wide variety of diseases and disorders. In recent investigations, Peripheral Stimulation (PS) (i.e., stimulation of nerve tissue outside of the spinal cord and brain), which includes Peripheral Nerve Field Stimulation (PNFS) techniques that stimulate nerve tissue directly at the symptomatic site of the disease or disorder (e.g., at the source of pain), and Peripheral Nerve Stimulation (PNS) techniques that directly stimulate bundles of peripheral nerves that may not necessarily be at the symptomatic site of the disease or disorder, has demonstrated efficacy in the treatment of chronic pain syndromes (e.g., painful peripheral neuropathy (PN), post-herpetic neuralgia (PHN), fibromyalgia syndrome (FMS), failed back surgery syndrome (FBSS), Arachnoiditis, occipital neuralgia, peripheral pelvic pain, cardiac pain, etc.) and incontinence, and a number of additional applications are currently under investigation.
An implantable neurostimulation system, whether used in the context of PS or another stimulation application, typically includes one or more electrode carrying stimulation leads, which are implanted at the desired stimulation site. In PS, the stimulation lead(s) are implanted in the subcutaneous tissues of a peripheral region, such as the lower back region, cervical region, arm, or leg. The implantable neurostimulation system further includes a neurostimulator (e.g., an implantable pulse generator (IPG)) implanted within a tissue pocket remotely from the stimulation site, but coupled to the stimulation lead(s). Thus, electrical pulses can be delivered from the neurostimulator to the stimulation lead(s) to stimulate or activate a volume of neural tissue. In particular, electrical energy conveyed between at least one cathodic electrode and at least one anodic electrodes creates an electrical field, which when strong enough, depolarizes (or “stimulates”) the neurons beyond a threshold level, thereby inducing the firing of action potentials (APs) that propagate along the neural fibers.
Stimulation energy may be delivered to the electrodes during and after the lead placement process in order to verify that the electrodes are stimulating the target neural elements and to formulate the most effective stimulation regimen. The regimen will dictate which of the electrodes are sourcing current pulses (anodes) and which of the electrodes are sinking current pulses (cathodes) at any given time, as well as the magnitude, duration, and rate of the current pulses. The stimulation regimen will typically be one that provides stimulation energy to all of the target tissue that must be stimulated in order to provide the therapeutic benefit, yet minimizes the volume of non-target tissue that is stimulated. In the case of PS, such a therapeutic benefit is accompanied by “paresthesia,” i.e., a tingling sensation that is effected by the electrical stimuli applied through the electrodes.
While PS has been generally useful in treating patients, there still remain issues. For example, an electrical field applied to a particular peripheral region may not only stimulate nerve endings that innervate a region local to the applied electrical field, but also stimulate neural axons that innervate tissue remote from the applied electrical field. As such, it is often difficult to selectively perform PNFS and PNS. That is, when PNFS is desired, PNS may inadvertently be performed instead of or in addition to PNS, and when PNS is desired, PNFS may inadvertently be performed instead of or in addition to PNS.
There, thus, remains a need for an improved technique to selectively perform PNFS and PNS in a patient.